Calculate the theoretical percentage of water in gypsum, rounded to the nearest whole number %. (calcium sulfate dihydrate; CaSO4 ° 2H2O; Ca = 40 g/mol, S= 32 g/mol; O= 16 g/mol; H= 1 g/mol).

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To calculate the theoretical percentage of water in gypsum (CaSO4 ° 2H2O), we need to determine the molar mass of water and gypsum separately.

The molar mass of water (H2O) can be calculated as follows:
(2 × 1 g/mol [hydrogen]) + (1 × 16 g/mol [oxygen]) = 18 g/mol

The molar mass of gypsum (CaSO4 ° 2H2O) can be calculated as follows:
(1 × 40 g/mol [calcium]) + (1 × 32 g/mol [sulfur]) + (4 × 16 g/mol [oxygen]) + (2 × 18 g/mol [water]) = 172 g/mol

Now, let's calculate the percentage of water in gypsum:

Percentage of water = (Molar mass of water / Molar mass of gypsum) × 100
= (18 g/mol / 172 g/mol) × 100
≈ 10.5%

Therefore, the theoretical percentage of water in gypsum is approximately 10.5%, rounded to the nearest whole number, which is 11%.

To calculate the theoretical percentage of water in gypsum (calcium sulfate dihydrate; CaSO4 · 2H2O), you need to determine the molecular weight of water and gypsum, and then use these values to calculate the percentage.

1. Molecular weight of water:
Water (H2O) consists of two hydrogen atoms (H) with a molecular weight of 1 g/mol and one oxygen atom (O) with a molecular weight of 16 g/mol. Therefore, the molecular weight of water is calculated as:
2(1 g/mol for H) + 16 g/mol for O = 18 g/mol.

2. Molecular weight of gypsum:
Gypsum (CaSO4 · 2H2O) consists of one calcium atom (Ca) with a molecular weight of 40 g/mol, one sulfur atom (S) with a molecular weight of 32 g/mol, four oxygen atoms (O) with a molecular weight of 16 g/mol each, and two water molecules (H2O) as described above with a total molecular weight of 18 g/mol. Therefore, the molecular weight of gypsum is:
40 g/mol for Ca + 32 g/mol for S + 4(16 g/mol for O) + 2(18 g/mol for H2O) = 172 g/mol.

3. Calculation of the theoretical percentage of water in gypsum:
To calculate the percentage, divide the molecular weight of water (18 g/mol) by the molecular weight of gypsum (172 g/mol) and multiply by 100 to get the percentage:
(18 g/mol ÷ 172 g/mol) × 100 = 10.47%.

Rounding this to the nearest whole number, the theoretical percentage of water in gypsum is approximately 10%.

%H2O = (mass H2O/mass CaSO4.2H2O)*100 = ?

Use molar masses for H2O and gypsum.